TIME-DEPENDENT INDUCTION OF 2 DISTINCT HEPATIC CYTOCHROME P4501A CATALYTIC ACTIVITIES AT LOW-TEMPERATURES IN ARCTIC CHARR (SALVELINUS-ALPINUS) AFTER ORAL-EXPOSURE TO BENZO(A)PYRENE

Due to increased industrial and other anthropogenic activities during the last decades, the arctic environment faces increasing levels of or ganic pollution. The presence of polycyclic aromatic hydrocarbons in t he arctic environment is of major concern because of their carcinogeni c potential and their effect on the health and reproductive performanc e of animals. There is an increasing demand for sensitive and relative ly inexpensive diagnostic biomarkers, applicable for environmental mon itoring in the Arctic seas to assess the human impact on the Arctic. A s a first step to validate the use of enzymatic assays in fish as an i ndicator for environmental pollution, the hepatic cytochrome P450 indu ction in the anadromous Spitsbergen Arctic charr was studied at severa l time intervals during 4 days following oral exposure to benzo(a)pyre ne. Three different enzyme activities were studied, i.e. testosterone- 6 beta-hydroxylation, the ethoxyresorufin-O-deethylation and the caffe ine-N3-demethylation. Both the ethoxyresorufin-O-deethylation and the caffeine-N3-demethylation activity (only the 1,7-dimethylxanthine meta bolite was formed) showed a strong and time-dependent induction after exposure, Western immunoblotting revealed an increase in the amount of protein. In the exposed groups a clear time-dependent increase of pro tein reacting with anti-cod CYP1A was observed. Between the ethoxyreso rufin-O-deethylation and the caffeine-N3-demethylation activity in the exposed animals there was a strong and linear correlation. There was no effect of benzo(a)pyrene exposure on the testosterone-6 beta-hydrox ylation. The slow and long lasting induction, probably due to the low water temperatures 5 degrees C, can be regarded as advantageous for bi omonitoring. Differences in inhibition (alpha-naphtaflavone, furafylli ne) characteristics between ethoxyresorufin-O-deethylation rate and ca ffeine-N3-demethylation rate could be interpreted in terms of possible presence of more than one P4501A isoform in this fish species.